set_play_mode · MCP For Unity MCP: Risk & Policy

WHAT IT DOES

What set_play_mode does on MCP For Unity

AI agents invoke set_play_mode to trigger actions in MCP For Unity. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why set_play_mode needs a policy

Toggling Play Mode triggers the Unity Editor to enter or exit a runtime simulation state, which is an external operation with side effects (reloading scene state, running scripts, potentially losing unsaved changes). It doesn't read data, write persistent data, or delete anything, but it executes a significant editor state change. Misuse could disrupt ongoing work or cause loss of unsaved scene edits.

From the tool's definition Enables or disables Play Mode in the Unity Editor

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_play_mode Rate-limited

set_play_mode stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_play_mode": {
      "limits": [
        {
          "counter": "set_play_mode_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP For Unity, so you can run agents against it safely.

FAQ

Questions about set_play_mode

What does the set_play_mode tool do? +

Enables or disables Play Mode in the Unity Editor. It is categorised as a Execute tool in the MCP For Unity MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on set_play_mode? +

Register the MCP For Unity MCP server in PolicyLayer and add a rule for set_play_mode: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP For Unity. Nothing to install.

What risk level is set_play_mode? +

set_play_mode is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit set_play_mode? +

Yes. Add a rate_limit block to the set_play_mode rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block set_play_mode completely? +

Set action: deny in the PolicyLayer policy for set_play_mode. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides set_play_mode? +

set_play_mode is provided by the MCP For Unity MCP server (yunuscan/mcpforunity). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.